Academic literature on the topic 'Nuclear and plasma physics not elsewhere classified'

Classification of processes in heavy-ion collisions in the CBM experiment (FAIR/GSI, Darmstadt) using neural networks is investigated. Fully-connected neural networks and a deep convolutional neural network are built to identify quark–gluon plasma simulated within the Parton-Hadron-String Dynamics (PHSD) microscopic off-shell transport approach for central Au+Au collision at a fixed energy. The convolutional neural network outperforms fully-connected networks and reaches 93% accuracy on the validation set, while the remaining only 7% of collisions are incorrectly classified.

Abstract The risk of radiation effects in children of individuals exposed to ionising radiation remains an ongoing concern for aged veterans of the British nuclear testing programme. The genetic and cytogenetic family trio (GCFT) study is the first study to obtain blood samples from a group of British nuclear test veterans and their families for the purposes of identifying genetic alterations in offspring as a consequence of historical paternal exposure to ionising radiation. In this report, we describe the processes for recruitment and sampling, and provide a general description of the study population recruited. In total, blood samples were received from 91 (49 test and 42 control) families representing veteran servicemen from the army, Royal Air Force and Royal Navy. This translated to an overall response rate of 14% (49/353) for test veterans and 4% (42/992) for control veterans (excluding responders known to be ineligible). Due to the lack of dose information available, test veterans were allocated to a three-point exposure rank. Thirty (61%) test veterans were ranked in the lower group. Nineteen (39%) of the 49 test veterans were classified in the mid (5 veterans; 10%)/high (14 veterans; 29%) exposure ranks and included 12 veterans previously identified as belonging to the special groups or listed in health physics documents. An increased number of test veteran families (20%), compared with control families (5%), self-reported offspring with congenital abnormalities (p = 0.03). Whether this observation in this small group is reflective of the entire UK test veteran cohort or whether it is selection bias requires further work. The cohort described here represent an important and unique family trio grouping whose participation is enabling genetic studies, as part of the GCFT study, to be carried out. The outcomes of these studies will be published elsewhere. ISRCTN Registry: 17461668.

Since 1979 the Fachinformationszentrum Karlsruhe produces the bibliographic database PHYS which covers the worldwide literature in physics. The database is available on STN International. The database contains about 1,2 million citations in all fields of physics ranging from mathematical physics, elementary particles and field theories, nuclear, atomic and molecular physics, optics, acoustics and fluid dynamics, plasma physics, condensed matter physics, materials science, physical chemistry and biophysics up to geophysics, astronomy and astrophysics. The annual update contains more than 120.000 citations. The database is updated bimonthly. All kinds of literature are included from journal articles, conference papers, books and reports up to dissertations. The citations in the database are in English, publications in other languages have translated English title and abstract. Astronomy and astrophysics are covered in PHYS completely as possible. In 1987 there were more than 21.000 citations in these fields. There are many citations which are classified in PHYS into other fields like atomic or plasma physics and optics and which are not numbered to astronomy but may have a specific relevance for astronomers.

The article discusses the process of plasma chemical synthesis of uranium-thorium oxide powders for a new generation dispersion nuclear fuel. In the course of research, the combustion parameters of the precursors were calculated. Precursors were water-organic nitrate solutions based on uranyl nitrate and thorium nitrate (fissile components), as well as magnesium nitrate (matrix material). The organic component of the solutions was acetone due to the sufficiently high calorific value and good mutual solubility. In the course of thermodynamic calculations, the optimal modes of processing of the water-organic nitrate solutions in low-temperature plasma were determined. These modes ensured the synthesis of oxide powders of the necessary stoichiometry without impurities of unoxidized carbon (soot). Experiments to obtain the samples of powders were carried out with the model solutions in which uranyl and thorium nitrates were replaced by neodymium and cerium ones, which are in the same group of the periodic table. The synthesis was carried out with the use of a plasma chemicalunit based on a high frequency torch plasmatron. The synthesized powders were subjected to a number of analyzes including electron microscopy, particle size analysis, X-ray phase analysis and BET analysis. The results showed that the powders can be classified as nanosized.

Abstract Indonesia has natural graphite reserved in Sulawesi, Sumatera and Kalimantan islands. The highest graphite content was observed in Sanggau Region, West Kalimantan. Indonesian natural graphite has the potential to be used as fuel matrix in Pebble Bed Reactor (PBR) type - High Temperature Gas Cooled Reactor (HTGR). To increase self-reliance of graphite supply and decrease graphite import for fuel matrix purposes, it is necessary to master the purification technology of graphite. Graphite matrix in Pebble Bed Reactor (PBR) fuel has an important role. It is not only used as neutron moderator and structural material to protect nuclear fuel but also as heat transfer media. Therefore, the graphite matrix must meet the physical and chemical criteria specified for PBR fuel. This paper focuses on current status of purification of Indonesian natural graphite as a candidate for nuclear fuel matrix using hydrometallurgy and pyrometallurgy. Acid and acid mixtures such as HF, HNO3+H2SO4 and HF+HCl+H2SO4 were used for the hydromet-allurgy purification process, while Arc Plasma System were used for pyrometallurgy methods. Characterization for the purified graphite includes physical and chemical properties. The result showed that Indonesian natural graphite obtained from hydrometallurgy was classified into low nuclear grade graphite but it still could be used as nuclear fuel matrix PBR - HTGR. The graphitization degree needs to be increased and the impurity content needs to be decreased for the purified Indonesian graphite using hydrometallurgy method. The Indonesian natural graphite obtained from preliminary pyrometallurgy methods has 96.78 % graphite content according to SEM (surface) observation and the graphite content needs to be increased into nuclear grade graphite.

Bridging the gap between the classical and quantum regimes has consequences not only for fundamental tests of quantum theory, but for the relation between quantum mechanics and gravity. The field of levito-dynamics provides a promising platform for testing the hypotheses of the works investigating these ideas. By manipulating a macroscopic particle's motion to the scale of its ground state wavefunction, levito-dynamics offers insight into the macroscopic-quantum regime.

Ardent and promising research has brought the field of levito-dynamics to a state in which these tests are available. Recent work has brought a mesoscopic particle's motion to near the ground state. Several factors of decoherence are limiting efficient testing of these fundamental theories which implies the need for alternative strategies for achieving the same goal. This thesis is concerned with investigating alternative methods that may enable a mesoscopic particle to reach the quantum regime. 

In this thesis, three theoretical proposals are studied as a means for a mesoscopic particle to reach the quantum regime as well as a detailed study into one of the most important factors of heating and decoherence for optical trapping. The first study of cooling a particle's motion highlights that the rotational degrees of freedom of a levitated symmetric-top particle leads to large harmonic frequencies compared to the translational motion, offering a more accessible ground state temperature after feedback cooling is applied. An analysis of a recent experiment under similar conditions is compared with the theoretical findings and found to be consistent. 

The second method of cooling takes advantage of the decades long knowledge of atom trapping and cooling. By coupling a spin-polarized, continuously Doppler cooled atomic gas to a magnetic nanoparticle through the dipole-dipole interaction, motional energy is able to be removed from the nanoparticle. Through this method, the particle is able to reach near its quantum ground state provided the atoms are at a temperature below the nanoparticle ground state temperature and the atom number is sufficiently large.
The final investigation presents the dynamics of an optically levitated dielectric disk in a Gaussian standing wave. Though few studies have been performed on disks both theoretically and experimentally, our findings show that the stable couplings between the translational and rotational degrees of freedom offer a possibility for cooling several degrees of freedom simultaneously by actively cooling a single degree freedom.

The safety and security of a radiological facility shares a common objective which is to ensure the protection of the population and the environment from an undue radiological hazard. Adapting and extending risk assessment to security applications has been limited because of the adaptive nature of the sub-state actors and the lack of historical data of terrorist attacks on radiological facilities. Currently, no broad risk index exists for radiological facilities, such as healthcare centers and universities. This study develops a quantitative risk-based methodology that radiological facilities can employ to conduct self-assessments and gain better understanding of the threat they face. The computation of the Potential Facility Risk Index (PFRI) is based on the triplet definition (threat, vulnerability, and consequences) of risk. The threat component of the PFRI is devised as a utility function weighing the threat group attributes and asset preference. The principles of probabilistic risk assessment and pathway analysis are implemented to account for radioactive material theft probabilities in different attack scenarios. Locational hazards and nuclear security culture are measured as a function of radiological facility vulnerability. The consequences of loss of life and economic loss are computed, as a result of an attack from the radiological dispersal device (RDD). The methodology is applied to a hypothetical healthcare facility a single radioactive with three material assets (⁶⁰Co, ¹³⁷Cs, ¹⁹²Ir). The representation of the PFRI value on a qualitative scale-ranging from “very low risk” (1) to “very high risk” (10) presents a holistic view of the state of the facility risk to RDD. The PFRI may be used by decision makers to evaluate any security upgrades and justify security investments. The RDD game, developed as an extension to PFRI, provides the healthcare facility (defender) with strategic options to budget scarce security resources and make optimal choices under severe uncertainty about the terrorist adversary (attacker) theat.

Weak interactions in an atomic system by external electromagnetic fields or nucleon-nucleon interaction cause perturbations in the wave-function and energy levels of electrons, which allow for transitions that are otherwise forbidden. Of particular interest are magnetic dipole (M1) transitions, Stark-induced transitions, and parity non-conserving (PNC) transitions. The PNC interaction in the hyperfine ground states is dominantly due to the anapole moment of the nucleus and there has been up-to-date only one such measurement carried out in any system; the Boulder group's ground-breaking measurement of the anapole moment in atomic cesium in 1997. Their result derived from two different hyperfine transitions, however, did not agree with the meson-coupling model from high energy physics experiments. Therefore, it is important to revisit the anapole moment through another method to cross-check the Boulder group's measurement. Our goal is to excite the nuclear-spin-dependent (NSD) PNC ground hyperfine transitions in cesium via radio-frequency (rf) and Raman excitation to directly determine the anapole moment. I present our progress toward measurement of the NSD transition in an atomic Cs beam geometry. We have developed a broadband rf cavity resonator to strongly suppress the magnetic dipole (M1) transition while enhancing the forbidden PNC electric dipole (E1) transition. We employed an injection locking scheme to generate a pair of phase-coherent Raman lasers far detuned from the cesium D2 line (852 nm) with a 9.2 GHz frequency difference. I report various measurement data from atomic signal via rf and Raman excitation. In the next generation of measurements, we will carry out interference experiments between rf and Raman transitions by varying the phase relations of the rf and Raman lasers fields. Finally, based on the measurements, I discuss a novel robust measurement technique involving interference of the Raman, M1 and E_PNC contributions.

In the past two decades, great interest in weakly ionized plasmas sustained by high voltage nanosecond pulsed plasmas at high repetition rates has emerged. For such plasmas, the electron number density does not significantly decay between pulses, unlike the electron temperature. Such conditions are favorable to reconfigurable plasma antennas where the low electron temperature may enable the reduction of the Johnson–Nyquist thermal noise if an antenna is operated in the plasma afterglow. Moreover, it may be possible to sustain such conditions with RF pulses. Doing so could enable a plasma antenna that transmits the driving frequency when the pulse is applied and receives other frequencies with low thermal noise between pulses.

To study nanosecond pulsed plasmas, experiments were performed in a parallel-plate electrode configuration in argon and nitrogen gas at a pressure of several Torr and repetition frequencies of 30-75 kHz. To measure the time-resolved electron number density in the afterglow of each pulse, a custom 58.1 GHz homodyne microwave interferometer was constructed. The voltage and current measurements were made using a back current shunt (BCS). Initial analysis of the measured electron density in both plasmas indicated that the electron thermalization was much faster than the electron decay. In the nitrogen plasma, dissociative recombination with cluster ions was the dominant electron loss mechanism. However, the dissociative recombination rates of the electrons in the argon plasma suggested the presence of molecular impurities, such as water vapor. Therefore, to better understand the recombination mechanisms in argon plasma with trace amounts (0.1% or less by volume) of water vapor under the experimental conditions, a 0-D kinetic model was developed and fit to the experimental data. The influence of trace amounts of water on the electron temperature and density decay was studied by solving electron energy and continuity equations. It was found that in pure argon, Ar⁺ ions dominate while the electrons are very slow to thermalize and recombine. Including trace amounts of water impurities drastically reduces the time for electrons to thermalize and increases their rate of recombination.

In addition to large quasi-steady electron number densities and low electron temperature in the plasma afterglow, plasmas sustained by nanosecond pulses use a lower power budget than those sustained by RF or DC supplies. The efficiency of the power budget can be characterized by measuring the ionization cost per electron, defined as the ratio of the energy deposited in a pulse to the total number of electrons created. This was experimentally determined in air and argon plasmas at 2-10 Torr sustained by 1-7 kV nanosecond pulses at repetition frequencies of 0.1-30 kHz. The number of electrons were determined from the measured electron density through microwave interferometry and assuming a plasma volume equivalent to the volume between electrodes. The energy deposited was calculated from voltage and current measurements using both a BCS as well as high frequency resistive voltage divider and fast current transformer (FCT). It was found that the ionization cost in all conditions was within a factor of three of Stoletov’s point (the theoretical minimum ionization cost) and two orders of magnitude less than RF plasma.

Having shown that it is possible to generate high electron density, low electron temperature plasmas with nanosecond pulses, it was necessary to now create a plasma antenna prototype. Initially, commercial fluorescent light bulbs were used and ignited using surface wave excitation at various RF frequencies and powers. The S₁₁ of the antenna response was measured by a VNA through a novel coupling circuit, while the deposited power was measured using a bi-directional coupler. Next, a custom plasma antenna was created in which the pressure and gas composition could be varied. In addition to the S₁₁ and deposited power, the antenna gain, and the electron number density were also measured for a pure argon plasma antenna at pressures of 0.3-1 Torr. Varying the applied power shifts the antenna resonance frequency while increasing the excitation frequency caused an increase in measured electron density for the same deposited power. Initial tests using direct electrode excitation of a twin-tube integrated compact fluorescent light bulb with nanosecond pulses have successfully been achieved. Future efforts include designing the proper circuitry to time-gate out the large pulse voltage to facilitate safe antenna measurements in the plasma afterglow.